This invention relates to telecommunication networks which contain circuit and packet switch network elements, and more particularly to networks which route circuit based messages through a packet network.
Telecommunication networks are commonly classified as either packet based networks or circuit based networks. A packet based network, such as an asynchronous transfer mode (ATM) network, sends data in packets through the network to remote locations. The data to be sent is subdivided into individual packets of data with each packet having a unique identification (ID) and carrying its own destination address. In this way, packets can go by different routes and arrive in a different order than transmitted. The packet ID allows the data to be reassembled in the proper sequence at the receiving device.
A circuit based network provides communication in which a fixed bandwidth circuit is established from point to point through the circuit based network and dedicated for the duration of a telephone call. An example of a circuit based network is a public switch telephone network (PSTN) using Signaling System No. 7 (SS7). Signaling System No. 7 protocol has been mandated for out-of-band signaling communication involving telecommunication network elements and has been implemented worldwide. SS7 network elements are each uniquely identified by a Message Transfer Part (MTP) Signaling Point Code (PC). Network administrators set up routes through a SS7 network so that the network elements 25 can send Message Signal Units (MSUs) from any network element to an other network element in the telecommunication network. The messages in a SS7 circuit based network are routed out-of-band and used by network elements to assign and connect fixed bandwidth circuits called bearer channels for the duration of the telephone call.
A gateway is a network device that bridges or connects two incompatible networks together. A packet circuit gateway is a network device that connects a packet network and circuit network. The packet circuit gateway allows fixed bandwidth circuits of the circuit network to be connected with the virtual circuits of the packet network for seamless transfer of voice and data information across both networks.
Quality of service problems occur when transporting voice and data information from high availability telephonic circuit based network through a packet network to another high availability circuit based network. It is critical that the customers of a service provider have the ability to communicate through the telecommunication network. Moreover, there are federal (United States) and world (International Telecommunications Union -Telecommunications (ITU-T)) reporting requirements for SS7 failures (xe2x80x9coutagesxe2x80x9d) above a certain threshold. Therefore, if the packet network is between two SS7 circuit based networks, the packet based network and gateway devices are required to meet the same availability standards as the SS7 networks. However, gateway devices are typically not designed, like PSTN telephonic switches, for high availability.
In order to achieve the quality of service level of a SS7 network, additional redundancy and fault tolerance features must be designed into the gateway devices. This approach of redesigning gateway devices is undesirable because of the increased complexity required in the gateway devices and additional cost to the telecommunication service provider. Therefore, there is a need in the art to prevent disruption of telecommunication service while utilizing the gateway devices with a minimal increase in complexity to route telephone calls in a telecommunication network containing both circuit based networks and packet based networks.
The problems noted above are solved in accordance with the invention and a technical advance is achieved in the art, by using a virtual transport server (VTS) to work in conjunction with a packet circuit gateway to setup virtual connections for a circuit through the packet network. The VTS network entity has connections to both the telephonic switches in a circuit network and the packet network. The packet circuit gateway also has connections to both the circuit network and the packet network. Additionally, the VTS communicates with the packet circuit gateway via the packet network.
The VTS receives call setup messages from telephonic switches in the circuit network. The VTS processes the call setup messages and notifies another VTS at another side of the packet network that a call is being setup. Each VTS notifies the packet circuit gateway connecting the respective circuit network and packet network. In response to the VTSs notifications, the packet circuit gateways set up a virtual connection through the packet network and signal the circuit IDs to the VTS. The VTSs transmit the circuit IDs, over the circuit networks, to the telephonic switches. The telephonic switches use the circuit lDs to make a connection to the packet circuit gateways and the virtual circuit through the packet network. Thus, a connection is placed through both circuit networks and the packet network.